Hydrocarbon energy storage and release control systems and methods

ABSTRACT

An exhaust control system comprises an absorption rate estimation module, a desorption rate estimation module, a rate of change module, a release rate estimation module, and a fuel control module. The absorption rate estimation module estimates a hydrocarbon energy absorption rate of a component of an exhaust system. The desorption rate estimation module estimates a hydrocarbon energy desorption rate of the component. The rate of change module that determines a stored energy rate of change based on a difference between the hydrocarbon absorption and desorption rates. The release rate estimation module estimates a hydrocarbon energy release rate for the component based on the stored energy rate of change. The fuel control module controls a rate of fuel injection into the exhaust system upstream of an oxidation catalyst based on the hydrocarbon energy release rate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to United States Patent Application Nos.______ (Atty. Docket No. P009991-PTDE-DPH/8540P-001039) filed on [INSERTFILING DATE], and ______ (Atty. Docket No.P009996-PTDE-DPH/8540P-001040) filed on [INSERT FILING DATE]. Thedisclosures of the above applications are incorporated herein byreference in their entirety.

FIELD

The present disclosure relates to internal combustion engine systems andmore particularly to exhaust systems.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

An engine combusts a mixture of air and fuel to produce drive torque fora vehicle. Air is drawn into the engine through a throttle valve. Fuelprovided by one or more fuel injectors mixes with the air to form theair/fuel mixture. The air/fuel mixture is combusted within one or morecylinders of the engine. An engine control module (ECM) controls thetorque output of the engine.

Exhaust resulting from combustion of the air/fuel mixture is expelledfrom the engine to an exhaust system. The ECM may adjust one or moreengine parameters based on signals from sensors that measure parameterswithin the exhaust system, respectively. For example only, one or moretemperature sensors, exhaust flow rate sensors, oxygen sensors, and/orother suitable sensors may be implemented within the exhaust system.

Measurements from the sensors may enable the ECM to adjust one or moreengine parameters to adjust one or more of the measured parameterstoward desired parameters, respectively. As the number of sensorsimplemented in a vehicle increases, however, the cost of producing thevehicle also increases. The increased cost may be attributable to thesensors themselves, associated wiring and hardware, and research anddevelopment. Additionally, a vehicle producer may produce a number ofdifferent vehicles, and each of the different vehicles may have adifferent exhaust system configuration. Calibrating and adjustingsensors implemented for each different vehicle and exhaust system mayalso increase the production cost of a vehicle.

SUMMARY

An exhaust control system comprises an absorption rate estimationmodule, a desorption rate estimation module, a rate of change module, arelease rate estimation module, and a fuel control module. Theabsorption rate estimation module estimates a hydrocarbon energyabsorption rate of a component of an exhaust system. The desorption rateestimation module estimates a hydrocarbon energy desorption rate of thecomponent. The rate of change module that determines a stored energyrate of change based on a difference between the hydrocarbon absorptionand desorption rates. The release rate estimation module estimates ahydrocarbon energy release rate for the component based on the storedenergy rate of change. The fuel control module controls a rate of fuelinjection into the exhaust system upstream of an oxidation catalystbased on the hydrocarbon energy release rate.

An exhaust control method comprises estimating a hydrocarbon energyabsorption rate of a component of an exhaust system, estimating ahydrocarbon energy desorption rate of the component, determining astored energy rate of change based on a difference between thehydrocarbon absorption and desorption rates, estimating a hydrocarbonenergy release rate for the component based on the stored energy rate ofchange, and controlling a rate of fuel injection into the exhaust systemupstream of an oxidation catalyst based on the hydrocarbon energyrelease rate.

In still other features, the systems and methods described above areimplemented by a computer program executed by one or more processors.The computer program can reside on a tangible computer readable mediumsuch as but not limited to memory, nonvolatile data storage, and/orother suitable tangible storage mediums.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples areintended for purposes of illustration only and are not intended to limitthe scope of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a functional block diagram of an exemplary engine systemaccording to the principles of the present disclosure;

FIG. 2 is a functional block diagram of an exemplary exhaust systemaccording to the principles of the present disclosure;

FIG. 3 is a functional block diagram of an exemplary exhaust controlmodule according to the principles of the present disclosure;

FIG. 4 is a functional block diagram of an exemplary storage moduleaccording to the principles of the present disclosure;

FIG. 5 is a functional block diagram of an exemplary oxidation gainestimation module according to the principles of the present disclosure;

FIG. 6 is a functional block diagram of an exemplary stored energyrelease compensation module according to the principles of the presentdisclosure; and

FIG. 7 is a flowchart depicting exemplary steps that may be performed bya method according to the principles of the present disclosure.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is in no wayintended to limit the disclosure, its application, or uses. For purposesof clarity, the same reference numbers will be used in the drawings toidentify similar elements. As used herein, the phrase at least one of A,B, and C should be construed to mean a logical (A or B or C), using anon-exclusive logical or. It should be understood that steps within amethod may be executed in different order without altering theprinciples of the present disclosure.

As used herein, the term module refers to an Application SpecificIntegrated Circuit (ASIC), an electronic circuit, a processor (shared,dedicated, or group) and memory that execute one or more software orfirmware programs, a combinational logic circuit, and/or other suitablecomponents that provide the described functionality.

An internal combustion engine generates drive torque through combustionof an air/fuel mixture. Exhaust resulting from combustion of theair/fuel mixture is expelled from the engine to an exhaust system. Theexhaust flows through components of the exhaust system before beingexpelled from the exhaust system. The exhaust system may treat theexhaust to reduce the amounts of one or more exhaust constituents beforethe exhaust is expelled from the exhaust system.

An exhaust control module estimates a rate at which energy is input to agiven one of the components of the exhaust system. The exhaust may gainand lose energy while flowing from an input to an output of thecomponent. For example only, the exhaust may lose energy via convection.The exhaust may also lose energy via conduction. The exhaust may gainenergy via oxidation of hydrocarbons of the exhaust.

The exhaust control module estimates a convective energy loss rate, aconductive energy loss rate, and an oxidation energy gain rateassociated with the component. The exhaust control module also estimatesan energy output rate for the component based on the energy input rate,the convective and conductive energy loss rates, and the oxidationenergy gain rate. The exhaust control module estimates a temperature ofthe exhaust output from the component based on the energy output rate.Estimating the temperatures of the exhaust at various locations in theexhaust system may reduce the production cost of a vehicle as one ormore temperature sensors may be omitted.

The component may absorb (i.e., store) hydrocarbons. Absorbedhydrocarbons may desorb (i.e., release) from the component. The exhaustcontrol module of the present disclosure estimates a rate of hydrocarbonenergy that is absorbed by the component and a rate of hydrocarbonenergy that is desorbed from the component. The exhaust control moduleestimates a stored energy rate of change based on the hydrocarbon energyabsorption and desorption rates.

The exhaust control module determines whether the component is releasinghydrocarbon energy based on the stored energy rate of change. When thecomponent is releasing hydrocarbon energy, the exhaust control moduleestimates the oxidation gain rate of the component based on an energyrelease rate. In this manner, the rate of energy output from thecomponent reflects the energy release rate.

Referring now to FIG. 1, a functional block diagram of an exemplaryimplementation of an engine system 100 is presented. An air/fuel mixtureis combusted within an engine 102 to produce drive torque for a vehicle.While the engine 102 will be discussed as a diesel-type engine, thepresent disclosure is applicable to other types of engines, such asgasoline-type engines and other suitable types of engines.

Air is drawn into the engine 102 through an intake manifold 104 and athrottle valve 106. The throttle valve 106 is actuated to control theflow of air into the engine 102. A throttle actuator module 108 controlsa flowrate of air through the throttle valve 106. For example only, thethrottle actuator module 108 may control opening of the throttle valve106.

A fuel actuator module 110 injects fuel that mixes with the air to formthe air/fuel mixture. The fuel actuator module 110 may inject the fuel,for example, into the intake manifold 104, near one or more intakevalves (not shown) associated a cylinder 112 of the engine 102, directlyinto the cylinder 112, or at another suitable location. For exampleonly, the fuel actuator module 110 may include one fuel injector (notshown) for each cylinder of the engine 102.

While only the single cylinder 112 is shown, the engine 102 may includemore than one cylinder. The cylinders may be arranged in one or morebanks of cylinders. The air/fuel mixture is combusted within thecylinders of the engine 102. Combustion of the air/fuel mixturegenerates drive torque and rotatably drives a crankshaft (not shown).

An engine control module (ECM) 130 controls the torque output of theengine 102. The ECM 130 may control the torque output of the engine 102based on driver inputs provided by a driver input module 132. The driverinput module 132 may generate the driver inputs based on an acceleratorpedal position, a brake pedal position, cruise control inputs, and othersuitable driver inputs.

The ECM 130 may control various engine actuators and various engineparameters to control the torque output of the engine 102. For exampleonly, the ECM 130 may control opening of the throttle valve 106, rate offuel injection, cylinder deactivation (e.g., the number of cylindersdeactivated), turbocharger boost, opening/closing of intake and exhaustvalves, and/or other engine parameters.

The ECM 130 may communicate with one or more modules or systems of avehicle. For example only, the ECM 130 may communicate with a hybridcontrol module 154 to coordinate operation of the engine 102 and one ormore electric motors, such as electric motor (EM) 156. The EM 156 mayalso function as a generator and may be used to selectively produceelectrical energy for use by vehicle electrical systems and/or forstorage in an energy storage device (not shown).

The ECM 130 selectively makes control decisions based on parametersmeasured by various sensors. For example, intake air temperature may bemeasured using an intake air temperature (IAT) sensor 140. Ambient airtemperature (T_(AMB)) may be measured using an ambient temperaturesensor 142. The mass flowrate of air through the throttle valve 106 maybe measured using a mass air flowrate (MAF) sensor 144.

A pressure within the intake manifold 104 may be measured using amanifold absolute pressure (MAP) sensor 146. In various implementations,engine vacuum may be measured, where the engine vacuum is determinedbased on a difference between ambient air pressure and the pressurewithin the intake manifold 104.

An engine coolant temperature (ECT) may be measured using an ECT sensor148. The ECT sensor 148 may be located within the engine 102 or atanother location where engine coolant is circulated, such as in aradiator (not shown). A vehicle speed sensor 150 measures a vehiclespeed. The vehicle speed sensor 150 may measure the vehicle speed basedon a transmission output shaft speed, a wheel speed, or another suitablemeasure of the vehicle speed.

Referring now to FIG. 2, a functional block diagram of an exemplaryexhaust system 200 that is associated with the engine 102 is presented.While the exhaust system 200 will be described as it is configured inFIG. 2, the present disclosure is applicable to other exhaust systemconfigurations which may include a fewer or greater number ofcomponents.

Exhaust resulting from combustion of the air/fuel mixture is expelledfrom the engine 102 to an exhaust manifold 202. An exhaust recirculation(EGR) system 204 may be implemented to selectively direct exhaust backto the intake manifold 104. The EGR system 204 may include an EGR valve206, a first EGR pipe 208, and a second EGR pipe 210. The EGR valve 206receives exhaust from the exhaust manifold 202 via the first EGR pipe208. The EGR valve 206 selectively directs exhaust from the exhaustmanifold 202 back to the intake manifold 104 via the second EGR pipe210.

Exhaust not directed by the EGR system 204 may flow from the exhaustmanifold 202 to a turbocharger 216. The turbocharger 216 providespressurized air to the intake manifold 104. More specifically, theturbocharger 216 includes a compressor (not shown in FIG. 1) that drawsin air, pressurizes the air, and provide the pressurized air to theintake manifold 104.

The turbocharger compressor may compress air drawn from the intakemanifold 104, from the environment, and/or from another suitable airsource. The turbocharger compressor is powered by the exhaust. Morespecifically, an impeller (not shown) of the turbocharger 216 isrotatably driven by the exhaust, and the impeller rotatably drives thecompressor. The turbocharger 216 may include variable geometrytechnology, variable vane technology, variable nozzle technology, and/orother suitable technology. The turbocharger 216 may include anotherturbocharger (e.g., a dual-turbocharger) and/or one or more additionalturbochargers may be included in the exhaust system 200.

A wastegate 214 may be selectively opened to allow exhaust to bypass theturbocharger 216. In this manner, the wastegate 214 may be used tocontrol the output (i.e., boost) of the turbocharger 216. The ECM 130may control the output of the turbocharger 216 via a boost actuatormodule 218. For example only, the boost actuator module 218 may controlthe output of the turbocharger 216 by controlling the wastegate 214, theextent to which the turbocharger 216 is in the path of the exhaust,and/or other suitable parameters. The boost actuator module 218 may alsocontrol opening of the EGR valve 206. The boost actuator module 218 maycontrol the turbocharger 216, the wastegate 214, and/or the EGR valve206 based on one or more signals from the ECM 130.

The exhaust may flow from the turbocharger 216 to a first exhaust pipe220. The exhaust may flow through the first exhaust pipe 220 to a firstconical frustum 222. The first conical frustum 222 may receive theexhaust at a top of the first conical frustum 222, and the exhaust mayflow toward a base of the first conical frustum 222. The first conicalfrustum 222 may include an increasing opening from the first exhaustpipe 220 to a first catalyst 224.

The first catalyst 224 includes an oxidation catalyst (OC). While othertypes of OCs may be included, the first catalyst 224 will be discussedas including a diesel oxidation catalyst (DOC). The DOC 224 may beimplemented within a housing that may be similar to the first exhaustpipe 220. The exhaust may flow through the DOC 224 to a second conicalfrustum 226.

The second conical frustum 226 may receive the exhaust at a base of thesecond conical frustum 226, and the exhaust may flow toward a top of thesecond conical frustum 226. The second conical frustum 226 may include adecreasing opening from the DOC 224 to a second exhaust pipe 228.

The exhaust may flow through the second exhaust pipe 228 to a thirdconical frustum 230. The third conical frustum 230 may receive theexhaust at a top of the third conical frustum 230, and the exhaust mayflow toward a base of the third conical frustum 230. The third conicalfrustum 230 may include an increasing opening from the second exhaustpipe 228 to a catalyst/filter unit 232.

The catalyst/filter unit 232 may include a catalyst 234 and aparticulate filter 236. While other types of catalysts and particulatefilters may be included, the catalyst 234 will be discussed as includinga selective catalytic reduction (SCR) catalyst, and the filter 236 willbe discussed as including a diesel particulate filter (DPF). The SCRcatalyst 234 and the DPF 236 may be implemented together within onehousing as shown in FIG. 2, or the SCR catalyst 234 and the DPF 236 maybe implemented within individual housings.

The exhaust may flow from the catalyst/filter unit 232, through a fourthconical frustum 238, to a third exhaust pipe 240. The fourth conicalfrustum 238 may receive the exhaust at a base of the fourth conicalfrustum 238, and the exhaust may flow toward a top of the fourth conicalfrustum 238. The fourth conical frustum 238 may include a decreasingopening from the catalyst/filter unit 232 to the third exhaust pipe 240.The exhaust system 200 may also include one or more additionalcomponents not shown in FIG. 2.

The exhaust system 200 may include a fuel actuator module 250 thatinjects fuel or another hydrocarbon providing fluid into the exhaustsystem 200 at a location upstream of the DOC 224. The fuel actuatormodule 250 may include one or more fuel injectors. Fuel injected intothe exhaust system 200 may vaporize. For example only, heat from theexhaust may cause injected fuel to vaporize. The DOC 224 oxidizeshydrocarbons, and the oxidation produces heat. The heat generated byhydrocarbon oxidation is directed downstream of the DOC 224 by the flowof the exhaust.

A dosing agent actuator module (not shown) may also be included thatinjects a dosing agent (e.g., urea) into the exhaust system 200. Thedosing agent actuator module may inject the dosing agent at a locationbetween the DOC 224 and the SCR catalyst 234. The SCR catalyst 234 mayselectively absorb ammonia (NH₃) provided by the dosing agent, and theammonia may react with nitrogen oxides (NOx) passing through the SCRcatalyst 234.

A percentage of the NOx of the exhaust that is removed from the exhaustvia reaction with ammonia may be referred to as the NOx conversionefficiency. The NOx conversion efficiency may be related to a storagecapacity of the SCR catalyst 234, and the storage capacity may beinversely related to a temperature of the SCR catalyst 234. A percentageof the HC converted (e.g., oxidized) by the DOC 224 may be referred toas the HC conversion efficiency. The HC conversion efficiency may berelated to exhaust temperature.

The DPF 236 may filter particulate from the exhaust passing through theDPF 236. Particulate filtered from the exhaust may accumulate within theDPF 236 over time. Particulate trapped within the DPF 236 may be removedfrom the DPF 236 through a process that may be referred to asregeneration.

Regeneration of the DPF 236 may involve clearing of trapped particulatefrom the DPF 236. Particulate may burn at temperatures greater than apredetermined temperature (e.g., approximately 600-800° C.). Heatgenerated via hydrocarbon oxidation upstream of the DPF 236 (e.g., bythe DOC 224) may be used to create the temperature conditions forregeneration.

The ECM 130 may include an exhaust control module 270 that controls theinjection of fuel into the exhaust system 200. For example only, theexhaust control module 270 may control a mass flowrate (e.g., g/s) atwhich the fuel is injected into the exhaust system 200 by the fuelactuator module 250. Fuel injected into the exhaust system 200 may bereferred to as post-combustion fuel as it is injected downstream of theengine 102.

The exhaust control module 270 and/or the ECM 130 may make controldecisions based on signals from one or more sensors. The exhaust system200 may include a turbo outlet temperature sensor 280, an oxygen sensor282, and an exhaust flow rate (EFR) sensor 284. The turbo outlettemperature sensor 280 measures a temperature of the exhaust output fromthe turbocharger 216 and generates a turbo outlet temperature signal(T_(TURBO-OUT)) accordingly. In other words, the turbo outlettemperature sensor 280 measures temperature of the exhaust input to thefirst exhaust pipe 220.

The oxygen sensor 282 measures oxygen concentration of the exhaust inputto the first exhaust pipe 220 and generates an 02 signal based on theoxygen concentration. In other implementations, a lambda sensor (notshown) may be implemented, and the oxygen sensor 282 may be omitted. TheEFR sensor 284 measures a mass flowrate of the exhaust input to thefirst exhaust pipe 220 and generates an EFR signal accordingly.

While the exhaust control module 270 is shown and discussed as beinglocated within the ECM 130, the exhaust control module 270 may belocated in another suitable location, such as external to the ECM 130.The exhaust control module 270 determines a rate of energy input to agiven component. The exhaust control module 270 also estimates an energyloss rate attributable to conduction and an energy loss rateattributable to via convection. The exhaust control module 270 may alsoestimate an energy gain rate attributable to hydrocarbon oxidation forthe component.

The exhaust control module 270 estimates a net energy output rate fromthe given component based on the rate of energy input to the component,the convective energy loss rate, the conductive energy loss rate, andthe oxidation energy gain rate. The exhaust control module 270 estimatesa temperature of the exhaust output from the component based on the netrate of energy output from the component.

The exhaust control module 270 may use the temperature and the netenergy output rate the component as the temperature and input energyrate of a next component. The exhaust control module 270 may estimate aconvective energy loss rate, a conductive energy loss rate, an oxidationenergy gain rate, a net output energy rate, and an outlet temperaturefor the next component, and so on.

The exhaust control module 270 may additionally or alternativelyestimate a net energy of exhaust at a desired location between an inletand an outlet of a component, such as within the DPF 236. The exhaustcontrol module 270 may estimate the net energy at the desired locationbased on the energy input rate of the component, a convective loss ratebetween the inlet and the desired location, a conductive loss ratebetween the inlet and the desired location, and an oxidation gain ratebetween the inlet and the desired location. The exhaust control module270 may estimate a temperature of the exhaust at the desired locationbased on the net energy at the desired location. The exhaust controlmodule 270 may control one or more parameters based on one or more ofthe temperatures.

Referring now to FIG. 3, a functional block diagram of an exemplaryimplementation of the exhaust control module 270 is presented. Theexhaust control module 270 may include an input energy module 302, astorage module 306, a convection loss estimation module 310, aconduction loss estimation module 314, and an oxidation gain estimationmodule 318. The exhaust control module 270 may also include a kineticenergy module 322, a net energy determination module net energy outputmodule 326, a temperature estimation module 334, a time constantdetermination module 338, and an EFR estimation module 342. The exhaustcontrol module 270 may also include a loss determination module 346 anda total loss determination module 350.

The input energy module 302 estimates a rate of energy input to thefirst exhaust pipe 220 and may estimate a rate of energy input to eachof the components implemented downstream of the first exhaust pipe 220.The first exhaust pipe 220 and the components implemented downstream ofthe first exhaust pipe 220 will be collectively referred to hereafter ascomponents 220-240.

The input energy module 302 may determine the input energy rate of agiven one of the components 220-240 based on a temperature of theexhaust input to the component, the EFR into the component, and aspecific heat of the exhaust input to the component. For example only,the input energy module 302 may determine the input energy rate (e.g.,J/s) of a given one of the components 220-240 using the equation:

$\begin{matrix}{{E_{IN} = \frac{T_{G}}{C_{G}*E\; F\; R}},} & (1)\end{matrix}$

where E_(IN) is the rate of energy input to the component, T_(G) is thetemperature of the exhaust input to the component, C_(G) is the specificheat of the exhaust input to the component, and EFR is the mass flowrate of the exhaust input to the component. For the first exhaust pipe220, T_(G) may be the turbo outlet temperature and EFR may be the EFRmeasured by the EFR sensor 284. The input energy module 302 may storethe input energy rates by component within the storage module 306.

The specific heats of the exhaust input to each of the components220-240 may be determined by the convection loss estimation module 310.A more detailed discussion of the determination of the specific heatscan be found below in conjunction with the exemplary embodiments of FIG.4 and FIG. 5. In sum, the specific heats are corrected based on anoxygen concentration of the exhaust.

Each of the components 220-240 may be categorized into one of threegroups. For example only, each of the components 220-240 maycharacterized as a pipe, a brick, or a conical frustum. The first,second, and third exhaust pipes 220, 228, and 240 may be categorized aspipes. The first, second, third, and fourth conical frustums 220, 226,230, and 238 may be categorized as conical frustums. The DOC 224, theSCR catalyst 234, and the DPF 236 may be categorized as bricks. As theDOC 224, the SCR catalyst 234, and the DPF 236 are contained withinhousings, the DOC 224, the SCR catalyst 234, and the DPF 236 may also besaid to include both a brick and a pipe.

The convection loss estimation module 310 may determine a specific heatof the exhaust for each of the components 220-240. The convection lossestimation module 310 may determine the specific heat of the exhaustwithin a given one of the components 220-240 based on a temperature ofexhaust input to the component.

For the first exhaust pipe 220, for example, the convection lossestimation module 310 may determine the specific heat of the exhaustbased on the turbo outlet temperature. The temperature of the exhaustinput to a component implemented downstream of the first exhaust pipe220 may be equal to a temperature of exhaust output from anothercomponent implemented directly upstream of the component. For exampleonly, the temperature of exhaust input to the second exhaust pipe 228may be equal to the temperature of exhaust output from the secondconical frustum 226. The estimation of the temperature output from thecomponents is discussed in detail below. The convection loss estimationmodule 310 may store the specific heats by component within the storagemodule 306.

The convection loss estimation module 310 may estimate an energy lossrate attributable to convection for each of the components 220-240.While the energy loss rate attributable to convection is discussed asreferring to as a loss, the convective energy loss rate may be an energygain rate in some circumstances. For example only, the convection lossestimation module 310 may estimate a convective energy loss rate (e.g.,J/s) of a given one of the components 220-240, for example, using theequation:

E _(CV)=(T _(S) −T _(G))*A*h _(CV),   (2)

where E_(CV) is the convective energy loss rate, T_(S) is a temperatureof a surface area of the component where convection between the exhaustand the component occurs, T_(G) is the temperature of the exhaust inputto the component, A is the surface area of the component where theconvection occurs, and h_(CV) is a predetermined convection coefficient.

For a given brick, the convection loss estimation module 310 mayestimate one convective energy loss rate between the exhaust and thebrick and one convective energy loss rate between the exhaust and thehousing. For example only, the convection loss estimation module 310 maydetermine the convective energy loss rate for a brick based on a sum ofthe two convective energy loss rates.

The convection loss estimation module 310 may estimate the temperatureof the surface area of the given component (i.e., T_(S)), for example,based on an integral of:

$\begin{matrix}{\frac{E_{{CV} - L}}{V*D*C_{C}},} & (3)\end{matrix}$

where E_(CV-L) is the convective energy loss of the component during alast control loop, V is a volume of the component, D is the density ofthe component, and C_(C) is a predetermined specific heat of thecomponent. The convection loss estimation module 310 may also limit thetemperature of the surface area to between a predetermined minimumtemperature (e.g., 0 K) and a predetermined maximum temperature (e.g.,1500 K), inclusive.

The convection loss estimation module 310 may use equations (2) and (3)in estimating the convective loss rate of a given pipe, a given cone,and the housing of a given brick. For estimating a convection loss rateof a given brick, however, the convection loss estimation module 310 mayestimate the temperature of the surface area of the given brick, forexample, based on a result of an integral of:

$\begin{matrix}{\frac{E_{{CV} - L}}{m*C_{C}},} & (4)\end{matrix}$

where m is the mass of the brick and C_(C) is the predetermined specificheat of the brick.

Characteristics of each of the components 220-240 may be stored withinthe storage module 306 and may be retrieved from the storage module 306when needed. For example only, the surface area of each of thecomponents 220-240, the predetermined convection coefficient for each ofthe components 220-240, the volume of each of the components 220-240,the specific heat of each of the components 220-240, and other suitablecharacteristics that are not shown may be stored by component within thestorage module 306. The characteristics of each of the components220-240 may be stored, for example, before a vehicle leaves an assemblylocation.

The convection loss estimation module 310 and/or other modules mayretrieve component characteristics from the storage module 306 whenneeded. The convection loss estimation module 310 may store theconvection energy loss rates by component within the storage module 306.

The conduction loss estimation module 314 may estimate an energy lossrate attributable to conduction for each of the components 220-240. Forexample only, the conduction loss estimation module 314 may estimate aconductive energy loss rate (e.g., J/s) for a given one of thecomponents 220-240 using the equation:

$\begin{matrix}{{E_{CD} = {{- k}*A*\frac{\Delta \; T}{x}}},} & (5)\end{matrix}$

where E_(CD) is the conductive energy loss rate of the component, k is apredetermined conductive coefficient of the component, A is a surfacearea of the given component between two heat fields, ΔT is a temperaturedifference between the temperature of the exhaust input to the componentand an environmental temperature, and x is a thickness of the componentbetween the two heat fields. The environmental temperature is discussedin more detail below.

For a given brick, the conductive loss estimation module 314 mayestimate one conductive energy loss rate between the brick and thehousing and one conductive energy loss rate between the housing and theenvironment. For example only, the conductive loss estimation module 314may determine the conductive energy loss rate for a brick based on a sumof the two conductive energy loss rates.

The conduction loss estimation module 314 may determine theenvironmental temperature by adjusting ambient temperature based on thevehicle speed. More specifically, the conductive loss estimation module314 may determine a temperature correction based on the vehicle speedand adjust the ambient temperature based on the temperature correctionto determine the environmental temperature. The conduction lossestimation module 314 may store the conduction energy loss rates bycomponent within the storage module 306.

Energy may be gained within one or more of the components 220-240 via HCoxidation. The HC that may be oxidized within a given component mayresult from combustion within the engine 102, may be provided by thefuel actuator module 250, may be slipped from an upstream component, mayhave desorbed from an upstream component, and/or from other suitablesources.

The oxidation gain estimation module 318 may estimate an oxidationenergy gain rate for each of the components 220-240. For example only,the oxidation gain estimation module 318 may estimate an oxidationenergy gain rate (e.g., J/s) of a given one of the components 220-240based on a conversion energy gain rate and a phase change energy lossrate.

The given component may gain oxidation energy via conversion (e.g.,oxidation) of HC. The rate of energy gained through HC conversion may bereferred to as the conversion energy gain rate. The given component maylose oxidation energy via changing the phase of fuel from a liquid intoa gas (i.e., vaporizing the fuel). The rate of energy lost to changingthe phase of fuel may be referred to as the phase change energy lossrate. The oxidation gain estimation module 318 may estimate theoxidation energy gain rate of a given one of the components 220-240based on a sum of the conversion energy gain rate and the phase changeenergy loss rate.

The oxidation gain estimation module 318 may also determine a fuel sliprate and an unvaporized HC output rate for each of the components220-240. The oxidation gain estimation module 318 may store theoxidation energy gain rates by component within the storage module 306.The oxidation gain estimation module 318 may also store the fuel sliprates and/or the unvaporized HC output rates by component within thestorage module 306. The oxidation gain estimation module 318 isdiscussed further below in conjunction with the exemplary embodiment ofFIG. 5.

The exhaust may gain or lose kinetic energy within some components, suchas within the first, second, third, and fourth conical frustums 222,226, 230, and 238. A kinetic energy gain may be attributable to, forexample, a reduction in opening area in the direction of the exhaustflow (and therefore a pressure increase). A kinetic energy loss may beattributable to an increase in opening area in the direction of theexhaust flow (and therefore a pressure decrease). For example only, theexhaust may lose kinetic energy within the first and third conicalfrustums 222 and 230, and the exhaust may gain kinetic energy within thesecond and fourth conical frustums 226 and 238.

The kinetic energy module 322 may determine an outlet temperature foreach of the conical frustums. The kinetic energy module 322 maydetermine an enthalpy of the exhaust flowing into a given conicalfrustum based on the temperature of the exhaust flowing into the conicalfrustum. The kinetic energy module 322 may also determine an enthalpychange based on a volumetric flowrate of the exhaust entering theconical frustum and the change in the opening area of the conicalfrustum. The kinetic energy module 322 may adjust the enthalpy based onthe enthalpy change and may convert the adjusted enthalpy into theoutlet temperature. The outlet temperature may be used by thetemperature estimation module 334, for example, in estimating oradjusting the outlet temperature of the conical frustums.

In some implementations, the kinetic energy gains or losses of theconical frustums may be negligible. Accordingly, the kinetic energymodule 322 may be omitted in some implementations in the interest ofmemory allocation and conservation of computational efficiency.

The net energy output module 326 may determine a net rate energy outputfrom each of the components 220-240 via the exhaust. The net energyoutput module 326 may determine a net energy rate (e.g., J/s) outputfrom a given one of the components 220-240 based on the rate of energyinput to the component, the convective energy loss rate of thecomponent, the conductive energy loss rate of the component, and theoxidation energy gain rate of the component. For example only, the netenergy output module 326 may determine the net energy output rate of thecomponent using the equation:

E _(NET) =E _(IN) +E _(O) +E _(CV) +E _(CD),   (6)

where E_(NET) is the net energy rate output from the component. E_(IN)is the rate of energy input to the component (positive). E_(O) is theoxidation energy gain rate within the component (positive or zero),E_(CV) is the convective energy loss rate of the component (positive ornegative), and E_(CD) is the conductive energy loss rate of thecomponent (generally negative).

The net energy output module 326 may store the net rates of energyoutput by component within the storage module 306. The net energy outputrate from one of the components 220-240 (i.e., the E_(NET)) may be usedas the rate of energy input to a next one of the components 220-240(i.e., the E_(IN)).

Based on the energy gains and losses upstream of a desired locationbetween an inlet and an outlet of a component, the net energy outputmodule 326 may determine the net energy rate at the desired location.For example only, the net energy output module 326 may determine the netenergy rate at the desired location using equation (6), where E_(IN) isthe input energy rate to the first exhaust pipe 220, E_(O) is a total ofthe oxidation energy gain rates upstream of the desired location, E_(CV)is a total of the convection energy loss rates upstream of the desiredlocation, and E_(CD) is a total of the conductive energy loss ratesupstream of the desired location. For another example only, the netenergy output module 326 may determine the net energy rate at thedesired location using equation (6), where E_(IN) is the input energyrate of the component, E_(O) is an oxidation energy gain rate betweenthe inlet of the component and the desired location, E_(CV) is aconvective energy loss rate between the inlet of the component and thedesired location, and E_(CD) is a conductive energy loss rate betweenthe inlet of the component and the desired location. When the desiredlocation is between the inlet and outlet of a component, thecharacteristics of the component upstream of the desired location, anaverage, or another suitable measure may be used.

The temperature estimation module 334 estimates a temperature of theexhaust at a location based on the net energy rate at the location. Thetemperature estimation module 334 may estimate the temperature of theexhaust output from a given one of the components 220-240 based on thenet energy rate output from the component. The temperature estimationmodule 334 may estimate the temperature of the exhaust at a desiredlocation between an inlet and an outlet of a component based on the netenergy rate at the desired location. For example only, the temperatureestimation module 334 may estimate the temperature of the exhaust at agiven location (T_(G-OUT)) of a component by integrating:

$\begin{matrix}{\frac{E_{NET}}{C_{G}*E\; F\; R},} & (7)\end{matrix}$

with respect to time and adjusting for a time constant of the component,where E_(NET) is the net energy rate at the location, C_(G) is thespecific heat of the exhaust input to the component, and EFR is the EFRof the exhaust input to the component.

The EFR estimation module 342 may estimate the EFR at the location basedon the EFR provided by the EFR sensor 284 and the characteristics of thecomponents 220-240 implemented upstream of the component. The EFRestimation module 342 may store the EFRs by component within the storagemodule 306.

The time constant determination module 338 may determine the timeconstant. The time constant determination module 338 may determine thetime constant for each of the components 220-240 and may store the timeconstants within the storage module 306 by component for use by thetemperature estimation module 334. For example only, the time constantdetermination module 338 may determine the time constant for a given oneof the components 220-240 using the equation:

$\begin{matrix}{{T = \frac{D*V*C_{C}}{h_{CV}*A}},} & (8)\end{matrix}$

where T is the time constant, D is the density of the component, V isthe volume of the component, C_(C) is the predetermined specific heat ofthe component, h_(CV) is the predetermined convection coefficient, and Ais the surface area of the component.

For a given brick, such as the DOC 224, the SCR catalyst 234, or the DPF236, the temperature estimation module 334 may additionally oralternatively estimate a temperature of the exhaust at a location withinthe brick. For example only, the estimate the temperature of the exhaustwithin a given brick using the equation:

$\begin{matrix}{{T_{G - B} = \frac{E_{IN} + E_{O}}{2*C_{G}*E\; F\; R}},} & (9)\end{matrix}$

where T_(G-B) is the temperature of the exhaust within the brick, E_(IN)is the rate of energy input to the brick, E_(O) is the oxidation energygain of the brick, C_(G) is the specific heat of the exhaust input tothe brick, and EFR is the EFR into the brick.

The temperature of the exhaust within a given brick may be used todetermine the conversion efficiency of the brick, and the conversionefficiency may be used in controlling one or more associated parameters.For example only, the HC conversion efficiency may be used incontrolling the rate of fuel injection by the fuel actuator module 250.The NOx conversion efficiency may be used in controlling the rate ofinjection of the dosing agent.

The loss determination module 346 determines an energy loss rateassociated with each of the components 220-240. For example only, theloss determination module 346 may determine an energy loss rate (e.g.,J/s) of a given one of the components 220-240 based on the convectiveenergy loss rate of the component, the conductive energy loss rate ofthe component, and the oxidation energy gain rate of the component. Forexample only, the loss determination module 346 may determine the energyloss rate of a given one of the components 220-240 using the equation:

E _(LOSS) =E _(O) +E _(CV) +E _(CD),   (10)

where E_(LOSS) is the energy loss rate of the component, E_(O) is theoxidation energy gain rate within the component (positive or zero),E_(CV) is the convective energy loss rate of the component (positive ornegative), and E_(CD) is the conductive energy loss rate of thecomponent (generally negative). The loss determination module 346 maystore the energy loss rates by component within the storage module 306.

The total loss determination module 350 determines a total energy lossrate upstream of a desired location based on the energy loss ratesupstream of the desired location. For example only, the total lossdetermination module 350 may determine a total energy loss rate (e.g.,J/s) at the desired location based on a sum of the energy loss ratesupstream of the desired location.

The desired location may be, for example, an inlet of the DPF 236. Thetotal loss determination module 350 may determine the total energy lossrate upstream of the inlet of the DPF 236 based on a sum of the energyloss rates of the first exhaust pipe 220, the first conical frustum 222,the DOC 224, the second conical frustum 226, the second exhaust pipe228, the third conical frustum 230, and the SCR catalyst 234.

The exhaust control module 270 may also include an SCR control module360 and a fuel control module 364. The SCR control module 360 maycontrol one or more exhaust system parameters. For example only, the SCRcontrol module 360 may control the injection rate of the dosing agent.The SCR control module 360 may control the injection rate of the dosingagent to, for example, maximize the amount of NOx removed from theexhaust (i.e., the conversion efficiency) and to minimize (or prevent)ammonia slip. Ammonia slip may refer to an amount of ammonia presentdownstream of the SCR catalyst 234.

The SCR control module 360 may also generate selectively requests forthe fuel control module 364. For example only, the SCR control module360 may request an increase or a decrease in the rate of injection offuel by the fuel actuator module 250. The SCR control module 360 mayrequest an increase or a decrease in the fuel injection rate to, forexample, control a temperature of the SCR catalyst 234.

The fuel control module 364 may control the mass flowrate of fuelinjected by the fuel actuator module 250 (e.g., g/s). For example only,the fuel control module 364 may control the fuel injection rate toadjust a temperature of the exhaust or a component to a targettemperature. For example only, the fuel control module 364 may controlthe fuel injection rate to achieve a target DPF temperature for aregeneration event of the DPF 236.

The fuel control module 364 may determine when to regenerate the DPF 236based on a mass of particulate trapped within the DPF 236 and/or othersuitable parameters. The mass of the particulate trapped within the DPF236 may be referred to as loading of the DPF 236. The loading of the DPF236 may be determined based on the EFR, a pressure drop across the DPF236, and/or other suitable parameters. The fuel control module 364 mayinitiate and perform regeneration of the DPF 236 when the loading isgreater than a predetermined loading and/or when other suitableconditions are satisfied.

The fuel control module 364 of the present disclosure may determine orreceive the target temperature. For example only, the fuel controlmodule 364 may receive a target temperature for a regeneration event ofthe DPF 236. The fuel control module 364 determines a temperaturedifference between the turbo outlet temperature measured by the turbooutlet temperature sensor 280 and the target temperature.

The fuel control module 364 estimates a target input energy rate basedon the temperature difference, the total energy loss rate upstream ofthe location, the specific heat of the exhaust at the location, and theEFR. The fuel control module 364 controls the rate of fuel injection bythe fuel actuator module 250 based on the target energy input rate. Inthis manner, the fuel control module 364 controls the fuel injectionrate of the fuel actuator module 250 to achieve the target temperatureat the location.

The fuel control module 364 controls the fueling rate in an open-loop.Open-loop control may refer to control of a parameter without receivingfeedback from a sensor measuring the parameter. For example only,open-loop control of the DPF input temperature may refer to control ofthe DPF input temperature without receiving feedback from a DPF inputtemperature sensor.

Referring now to FIG. 4, an exemplary diagram of an arrangement of datathat may be stored within the storage module 306 is presented. Thestorage module 306 may include an index of the components 220-240 andthe parameters associated with the components 220-240, respectively. Forexample only, characteristics, an EFR, an input temperature of theexhaust, a specific heat of the exhaust, an input energy rate, aoxidation energy gain rate, a convective energy loss rate, a conductiveenergy loss rate, a net output energy rate, and an outlet temperature ofthe exhaust may be stored for each of the components 220-240. Otherparameters may also be stored in the storage module 306 for each of thecomponents 220-240.

The exhaust temperature and energy rate input to a first component maybe equal to the exhaust temperature and the net rate of energy output,respectively, from a second component implemented directly upstream ofand providing exhaust to the first component. Written conversely, thenet rate of energy output and the exhaust temperature of the secondcomponent may be used as the input energy rate and exhaust temperature,respectively, of the first component, where the first component isimplemented directly downstream of the second component. Arrows havebeen included in FIG. 4 to illustrate this point.

Referring now to FIG. 5, a functional block diagram of an exemplaryimplementation of the oxidation gain estimation module 318 is presented.The oxidation gain estimation module 318 may include a conversionefficiency module 502, a slip determination module 506, and a conversionenergy gain estimation module 510. The oxidation gain estimation module318 may also include a fuel energy gain module 520, a phase change lossestimation module 524, a vaporization efficiency module 528, and anunvaporized HC output module 532.

The conversion efficiency module 502 may determine a conversionefficiency for each of the components 220-240. The conversion efficiencyof a given component may refer to the component's ability to convert(e.g., oxidize) HC. For a given one of the components 220-240, theconversion efficiency module 502 may estimate the conversion efficiencybased on a space velocity of the component and the temperature of theexhaust input to the component. For example only, the conversionefficiency may be a percentage expressed as a value between 0.0 and 1.0,inclusive. The space velocity of the component may be determined basedon a volumetric flow rate of the exhaust through the component and avolume of empty storage sites of the component.

For some components, such as pipes and conical frustums, the HCconversion efficiency may be small and may be negligible relative to theconversion efficiencies of bricks. Accordingly, the oxidation gainestimation module 318 may refrain from estimating the oxidation energygain rates for pipes and conical frustums in the interest of memoryallocation and conservation of computational efficiency.

The slip determination module 506 may determine a fuel slip rate of eachof the components 220-240. The fuel slip rate of a given component mayrefer to a mass flowrate (e.g., g/s) of fuel output from the component.For example only, the slip determination module 506 may determine thefuel slip rate of a given component using the equation:

Slip=(1−CE)*Fuel,   (11)

where Slip is the fuel slip rate, CE is the conversion efficiency, andFuel is the rate at which fuel is being supplied to the component. Thefuel slip rate of one of the components 220-240 may be used to determinethe rate at which fuel is being supplied to a next one of the components220-240. The slip determination module 506 may store the fuel slip ratesin the storage module 306 by component.

The conversion energy gain estimation module 510 may estimate aconversion energy gain rate for each of the components 220-240. Theconversion energy gain estimation module 510 may estimate the conversionenergy gain rate of a given one of the components 220-240 based on therate at which fuel is being supplied to the component, an energy contentof the fuel, and the conversion efficiency of the component. For exampleonly, the conversion energy gain estimation module 510 may estimate theconversion energy gain rate (e.g., J/s) of a given one of the components220-240 using the equation:

E _(CE) =CE*Fuel*HOC,   (12)

where E_(CE) is the conversion energy gain rate, CE is the conversionefficiency, fuel is the rate at which fuel is being supplied to thecomponent, and HOC is a predetermined heat of conversion of fuel. Forexample only, the heat of conversion may include a lower heating valueof fuel.

The fuel energy gain module 520 may estimate the oxidation energy gainrate of each of the components 220-240. The fuel energy gain module 520may estimate the oxidation energy gain rate (i.e., the E_(O)) of a givenone of the components 220-240 based on the conversion energy gain rateand a phase change energy loss rate of the component. For example only,the fuel energy gain module 520 may estimate the oxidation energy gainrate based on a sum of the conversion energy gain rate of the componentand the phase change energy loss rate of the component.

The phase change loss estimation module 524 may estimate the phasechange energy loss rate of each of the components 220-240. The phasechange loss estimation module 524 may estimate the phase change energyloss rate of a given one of the components 220-240 based on avaporization efficiency of the component and a flowrate of unvaporizedHC input to the component. The vaporization efficiency may refer to apercentage of HC vaporized within a component.

For example only, the phase change loss estimation module 524 mayestimate the phase change energy loss rate (e.g., J/s) of a given one ofthe components 220-240 using the equation:

E _(PC) =VE*HC _(IN)*HOV,   (13)

where E_(PC) is the phase change energy loss rate, VE is a vaporizationefficiency of the component, HC_(IN) is a mass flowrate of unvaporizedHC input to the component, and HOV is a predetermined heat ofvaporization. Unvaporized HC may be output by the engine 102, injectedby the fuel actuator module 250, and/or be provided by other sources.The mass flowrate of HC input to a given one of the components 220-240may be equal to a mass flowrate of HC output from another one of thecomponents 220-240 implemented upstream of the given component. The massflowrate of HC output from the components 220-240 is discussed below.

The vaporization efficiency module 528 may estimate the vaporizationefficiency (VE) for each of the components 220-240. The vaporizationefficiency module 528 may estimate the vaporization efficiency for agiven one of the components 220-240 based on the space velocity of thecomponent and the temperature of the exhaust input to the component. Forexample only, the vaporization efficiency may be a percentage expressedas a value between 0.0 and 1.0, inclusive.

The unvaporized HC output module 532 may estimate a rate of unvaporizedHC output from each of the components 220-240. For example only, theunvaporized HC output module 532 may estimate the rate of unvaporized HCoutput from a given one of the components 220-240 using the equation:

HC _(OUT)=(1−VE)*HC _(IN),   (14)

where HC_(OUT) is the mass flowrate of rate HC output from thecomponent, VE is the vaporization efficiency, and HC_(IN) is the rate atwhich HC is input to the component. The unvaporized HC output module 532may store the unvaporized HC output rates in the storage module 306 bycomponent.

The oxidation gain estimation module 318 may also include an energyrelease compensation module 550. The energy release compensation module550 may estimate a rate of HC energy absorbed by each of the components220-240, a rate of HC energy desorbed from each of the components220-240, and a stored energy rate of change for each of the components220-240. The energy release compensation module 550 may determinewhether one or more of the components 220-240 is in a releasing state.When in the releasing state, a given one of the components 220-240 isdesorbing (i.e., releasing) more HC energy than the component isabsorbing (i.e., storing).

The energy release compensation module 550 may estimate an energyrelease rate for each of the components 220-240 that are in thereleasing state. The energy release compensation module 550 may providethe energy release rates of the components 220-240 to the fuel energygain module 520 for use in determining the oxidation energy gain ratesof the components 220-240, respectively. For example only, the fuelenergy gain module 520 may sum the energy release rate with theconversion energy gain rate and the phase change energy loss rate indetermining the oxidation energy gain rate of a given one of thecomponents 220-240.

In this manner, the energy release rate is reflected in the oxidationenergy gain rate of the component. Accordingly, the energy release ratemay be accounted for when the fuel control module 364 controls the fuelinjection rate of the fuel actuator module 250 based on the total energyloss rate upstream of a location. Inadvertent over fueling that may beattributable to the release of HC energy may therefore be avoided. Overfueling may cause increased exhaust temperatures. The increased exhausttemperatures may damage one or more of the components 220-240 downstreamof where released HC oxidizes.

Referring now to FIG. 6, a functional block diagram of an exemplaryimplementation of the energy release compensation module 550 ispresented. The energy release compensation module 550 may include anabsorption ratio module 602, an absorption rate estimation module 606, adesorption rate estimation module 610, and a rate of changedetermination module 614. The energy release compensation module 550 mayalso include a stored energy estimation module 618, a statedetermination module 622, and a release rate estimation module 626.

The absorption ratio module 602 may estimate an HC absorption ratio foreach of the components 220-240. The absorption ratio module 602 mayestimate the HC absorption ratio of a given one of the components220-240 based on the space velocity of the component and the temperatureof the exhaust input to the component. The HC absorption ratio of eachof the components 220-240 may include a percentage expressed as a valuebetween 0.0 and 1.0, inclusive. The HC absorption ratio may approach 1.0as a rate at which the component is capable of absorbing HC approaches amaximum HC absorption rate.

The absorption rate estimation module 606 may estimate a HC energyabsorption rate of each of the components 220-240. The absorption rateestimation module 606 may estimate the HC energy absorption rate(E_(ABS)) of a given one of the components 220-240 based on the HCabsorption ratio of the component and the mass flowrate of HC into thecomponent (i.e., the HC_(IN)). For example only, the absorption rateestimation module 606 may estimate the HC energy absorption rate of thecomponent based on a product of the mass flowrate of HC into thecomponent and the HC absorption ratio of the component.

The desorption rate estimation module 610 may estimate a HC energydesorption rate of each of the components 220-240. The desorption rateestimation module 610 may estimate the HC energy desorption rate(E_(DES)) of a given one of the components 220-240 based on temperatureof the exhaust input to the component, the space velocity of thecomponent, and an amount of HC energy stored by the component. Forexample only, the amount of HC energy stored by the component may be anamount of HC energy stored by the component after a last control loop.The amount of HC energy stored by the component is discussed furtherbelow.

The rate of change determination module 614 may determine an energy rateof change for each for the components 220-240. The rate of changedetermination module 614 may determine the energy rate of change(E_(ROC)) for a given one of the components 220-240 based on the HCenergy absorption rate of the component and the HC energy desorptionrate of the component. For example only, the rate of changedetermination module 614 may determine the energy rate of change for thecomponent based on a difference between the HC energy absorption rateand the HC energy desorption rate. For example only, the difference maybe based on the HC energy absorption rate less the HC energy desorptionrate.

The stored energy estimation module 618 may estimate the amount of HCenergy stored by each of the components 220-240. The stored energyestimation module 618 may estimate the HC energy stored (E_(ST)) by agiven one of the components 220-240 based on the amount of HC energystored by the component after the last control loop and the energy rateof change. For example only, stored energy estimation module 618 mayestimate the amount of HC energy stored by the component based on a sumof on the amount of HC energy stored after the last control loop and aresult of an integral of the rate of change of the component withrespect to time.

The state determination module 622 may determine a state of each of thecomponents 220-240. The state determination module 622 may determine thestate of a given one of the components 220-240 based on the energy rateof change of the component. For example only, the state determinationmodule may determine that the component is in the releasing state whenthe energy rate of change is negative. Other states that a given one ofthe components 220-240 may be in may include, for example, a fullyabsorbed state or a fully desorbed state

The state determination module 622 may generate a state signal based onthe state of the component. For example only, the state determinationmodule 622 may set the state signal to an active state (e.g., 5 V) whenthe component is in the releasing state.

The release rate estimation module 626 may estimate a HC energy releaserate for each of the components 220-240 that are in the releasing state.The release rate estimation module 626 may also set a HC energy releaserate for the components 220-240 not in the releasing state to zero. Therelease rate estimation module may estimate the HC energy release ratefor a given one of the components 220-240 (E_(RELEASE)) that is in thereleasing state based on the energy rate of change of the component.

As shown in FIG. 5, the fuel energy gain module 520 may receive the HCenergy release rate, the conversion energy gain rate, and the phasechange energy loss rate for each of the components 220-240. The fuelenergy gain module 520 may estimate the oxidation energy gain rates forthe components 220-240 based on the HC energy release rates, theconversion energy gain rates, and the phase change energy loss rates ofthe components 220-240, respectively. For example only, the fuel energygain module 520 may estimate the oxidation energy gain rate of a givenone of the components 220-240 based on a sum of the HC energy releaserate of the component, the phase change energy loss rate of thecomponent, and the conversion energy gain rate of the component.

The HC energy release rate may therefore be taken into account (via theoxidation energy gain rate) in determining the energy output rate of thecomponent. Accordingly, a next component that receives the exhaust fromthe component may have a greater energy input rate (i.e., the E_(IN))than it would if the component was not releasing HC energy.

The HC energy release rate may therefore be taken into account indetermining the total energy loss rate upstream of a location. Asdiscussed above, the fuel control module 364 may control the fuelinjection rate of the fuel actuator module 250 based on the total energyloss rate to adjust the exhaust temperature at the location toward atarget temperature.

More specifically, the fuel control module 364 may determine a targetinput energy rate based on the total energy loss rate. The fuel controlmodule 364 may determine the target input energy rate further based onthe target temperature, the temperature of the exhaust input to thefirst exhaust pipe 220, the EFR, and the specific heat of the exhaust.For example only, the fuel control module 364 may determine the targetinput energy rate (e.g., J/s) using the equation:

E _(TARGET) =C _(G) *EFR*(T _(TARGET) −T _(G))−E _(LOSS-TOT),   (15)

where E_(TARGET) is the target input energy rate, C_(G) is the specificheat of the exhaust input to the component, T_(TARGET) is the targettemperature, T_(G) is the temperature of the exhaust input to the firstexhaust pipe 220, and E_(LOSS-TOT) is the total energy loss rateupstream of the location.

In sum, the fuel actuator module 250 may selectively reduce the fuelinjection rate based on the HC energy release rate. Reducing the fuelinjection rate based on the HC energy release rate may prevent theexhaust temperature at the location from exceeding the targettemperature.

Referring now to FIG. 7, a flowchart depicting exemplary steps 700 thatmay be performed by a method are presented. Control may begin in step702 where control may determine the HC absorption ratio for a given oneof the components 220-240. Control may determine the HC absorption ratiobased on the space velocity of the component and the temperature of theexhaust input to the component.

Control may estimate the HC energy absorption rate of the component instep 706. Control may determine the HC energy absorption rate based onthe HC absorption ratio and the mass flowrate of HC into the component.Control may estimate the HC energy desorption rate of the component instep 710. Control may estimate the HC energy desorption rate of thecomponent based on the temperature of the exhaust input to thecomponent, the space velocity of the component, and an amount of HCenergy stored by the component after a last control loop.

Control may determine the stored energy rate of change of the componentin step 714. Control may determine the stored energy rate of changebased on the HC energy absorption rate less the HC energy desorptionrate. Control may determine whether the component is in the releasingstate in step 718. If false, control may transfer to step 722; if true,control may continue in step 726. Control may determine that thecomponent is in the releasing state, for example, when the energy rateof change is negative.

In step 722 (i.e., when the component is not in the releasing state),control may estimate the oxidation energy gain rate of the componentbased on the phase change energy loss rate and the conversion energygain rate. Control may then continue to step 734, which is discussedfurther below.

In step 726 (i.e., when the component is in the releasing state),control may estimate the HC energy release rate of the component.Control may estimate the HC energy release rate based on the energy rateof change. Control may estimate the oxidation energy gain rate based onthe HC energy release rate in step 730. For example only, control mayestimate the oxidation energy gain rate of the component based on a sumof the HC energy release rate, the conversion energy gain rate, and thephase change energy loss rate. Control may continue to step 734.

In step 734, control may determine the energy loss rate of thecomponent. Control may determine the energy loss rate of the componentbased on a sum of the convective energy loss rate, the conductive energyloss rate, and the oxidation energy gain rate. Control may determine thetotal energy loss rate upstream of a location based on the energy lossrate of the component and energy loss rates upstream of the location instep 738. For example only, control may determine the total energy lossrate upstream of the location based on a sum of the energy loss ratesupstream of the location.

Control controls the fuel injection rate of the fuel actuator module 250based on the total energy loss rate in step 742. For example only,control may determine a target input energy rate based on the totalenergy loss rate using equation (15), as discussed above, and controlmay control the fuel injection rate of the fuel actuator module 250based on the target input energy rate. In this manner, control suppliesfuel to the DOC 224 based on the target input energy rate to adjust thetemperature of the exhaust at the location toward the targettemperature. While control is shown as ending after step 742, controlmay instead return to step 702. In other words, the exemplary steps 700may be illustrative of one control loop, and more than one control loopmay be performed.

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the disclosure can beimplemented in a variety of forms. Therefore, while this disclosureincludes particular examples, the true scope of the disclosure shouldnot be so limited since other modifications will become apparent to theskilled practitioner upon a study of the drawings, the specification,and the following claims.

1. An exhaust control system comprising: an absorption rate estimationmodule that estimates a hydrocarbon energy absorption rate of acomponent of an exhaust system; a desorption rate estimation module thatestimates a hydrocarbon energy desorption rate of the component; a rateof change module that determines a stored energy rate of change based ona difference between the hydrocarbon absorption and desorption rates; arelease rate estimation module that estimates a hydrocarbon energyrelease rate for the component based on the stored energy rate ofchange; and a fuel control module that controls a rate of fuel injectioninto the exhaust system upstream of an oxidation catalyst based on thehydrocarbon energy release rate.
 2. The exhaust control system of claim1 further comprising an absorption ratio module that estimates anabsorption ratio of the component based on a temperature of exhaustinput to the component and a space velocity of the component, whereinthe absorption rate estimation module estimates the hydrocarbon energyabsorption rate based on the absorption ratio.
 3. The exhaust controlsystem of claim 2 wherein the absorption rate estimation moduleestimates the hydrocarbon energy absorption rate further based on a massflowrate of hydrocarbons into the component.
 4. The exhaust controlsystem of claim 2 wherein the absorption rate estimation moduleestimates the hydrocarbon energy absorption rate based on a product ofthe absorption ratio and a mass flowrate of hydrocarbons into thecomponent.
 5. The exhaust control system of claim 1 wherein thedesorption rate estimation module estimates the hydrocarbon energydesorption rate based on a temperature of the exhaust input to thecomponent, a space velocity of the component, and an amount ofhydrocarbon energy stored by the component.
 6. The exhaust controlsystem of claim 5 further comprising a stored energy estimation modulethat estimates the amount of hydrocarbon energy stored by the componentbased on the stored energy rate of change.
 7. The exhaust control systemof claim 6 wherein the stored energy estimation module estimates theamount of hydrocarbon energy stored by the component further based on aprevious amount of hydrocarbon energy stored by the component.
 8. Theexhaust control system of claim 1 further comprising a statedetermination module that determines when the component is in an energyreleasing state based on the stored energy rate of change.
 9. Theexhaust control system of claim 8 wherein the state determination moduledetermines that the component is in the energy releasing state when thehydrocarbon energy desorption rate is greater than the hydrocarbonenergy absorption rate.
 10. The exhaust control system of claim 1further comprising: an oxidation gain estimation module that estimatesan oxidation energy gain rate of the component based on the hydrocarbonenergy release rate; a loss determination module that determines anenergy loss rate of the component based on the oxidation energy gainrate, a conducive energy loss rate associated with the component, and aconvective energy loss rate associated with the component; and a totalloss determination module that determines a total energy loss rateupstream of a location in the exhaust system based on the energy lossrate of the component, wherein the fuel control module controls the fuelinjection rate based on the total energy loss rate and a targettemperature for the location.
 11. An exhaust control method comprising:estimating a hydrocarbon energy absorption rate of a component of anexhaust system; estimating a hydrocarbon energy desorption rate of thecomponent; determining a stored energy rate of change based on adifference between the hydrocarbon absorption and desorption rates;estimating a hydrocarbon energy release rate for the component based onthe stored energy rate of change; and controlling a rate of fuelinjection into the exhaust system upstream of an oxidation catalystbased on the hydrocarbon energy release rate.
 12. The exhaust controlmethod of claim 11 further comprising: estimating an absorption ratio ofthe component based on a temperature of exhaust input to the componentand a space velocity of the component; and estimating the hydrocarbonenergy absorption rate based on the absorption ratio.
 13. The exhaustcontrol method of claim 12 further comprising estimating the hydrocarbonenergy absorption rate further based on a mass flowrate of hydrocarbonsinto the component.
 14. The exhaust control method of claim 12 furthercomprising estimating the hydrocarbon energy absorption rate based on aproduct of the absorption ratio and a mass flowrate of hydrocarbons intothe component.
 15. The exhaust control method of claim 11 furthercomprising estimating the hydrocarbon energy desorption rate based on atemperature of the exhaust input to the component, a space velocity ofthe component, and an amount of hydrocarbon energy stored by thecomponent.
 16. The exhaust control method of claim 15 further comprisingestimating the amount of hydrocarbon energy stored by the componentbased on the stored energy rate of change.
 17. The exhaust controlmethod of claim 16 further comprising estimating the amount ofhydrocarbon energy stored by the component further based on a previousamount of hydrocarbon energy stored by the component.
 18. The exhaustcontrol method of claim 11 further comprising determining when thecomponent is in an energy releasing state based on the stored energyrate of change.
 19. The exhaust control method of claim 18 furthercomprising determining that the component is in the energy releasingstate when the hydrocarbon energy desorption rate is greater than thehydrocarbon energy absorption rate.
 20. The exhaust control method ofclaim 11 further comprising: estimating an oxidation energy gain rate ofthe component based on the hydrocarbon energy release rate; determiningan energy loss rate of the component based on the oxidation energy gainrate, a conducive energy loss rate associated with the component, and aconvective energy loss rate associated with the component; determining atotal energy loss rate upstream of a location in the exhaust systembased on the energy loss rate of the component; and controlling the fuelinjection rate based on the total energy loss rate and a targettemperature for the location.